Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$89.75	13.713%	$102.0574	$102.06	$102.05	$102.10
Purchase #2	$108.79	5.118%	$114.3579	$114.36	$114.35	$114.40
Purchase #3	$164.48	6.585%	$175.311	$175.31	$175.30	$175.30
Purchase #4	$244.86	12.465%	$275.3818	$275.38	$275.40	$275.40
Purchase #5	$97.45	6.268%	$103.5582	$103.56	$103.55	$103.60
Purchase #6	$227.59	12.175%	$255.2991	$255.30	$255.30	$255.30
Purchase #7	$212.87	11.874%	$238.1462	$238.15	$238.15	$238.10
7 purchase totals =	$1,145.79		$1,264.1116	$1,264.12	$1,264.10	$1,264.20