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	$106.32	5.818%	$112.5057	$112.51	$112.50	$112.50
Purchase #2	$183.25	4.564%	$191.6135	$191.61	$191.60	$191.60
Purchase #3	$75.41	5.492%	$79.5515	$79.55	$79.55	$79.60
Purchase #4	$106.72	4.163%	$111.1628	$111.16	$111.15	$111.20
Purchase #5	$109.35	13.755%	$124.3911	$124.39	$124.40	$124.40
Purchase #6	$102.35	9.727%	$112.3056	$112.31	$112.30	$112.30
Purchase #7	$49.30	7.116%	$52.8082	$52.81	$52.80	$52.80
7 purchase totals =	$732.70		$784.3384	$784.34	$784.30	$784.40