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	$93.99	7.639%	$101.1699	$101.17	$101.15	$101.20
Purchase #2	$81.56	9.629%	$89.4134	$89.41	$89.40	$89.40
Purchase #3	$212.54	7.384%	$228.234	$228.23	$228.25	$228.20
Purchase #4	$55.53	6.863%	$59.341	$59.34	$59.35	$59.30
Purchase #5	$166.98	6.637%	$178.0625	$178.06	$178.05	$178.10
Purchase #6	$98.69	4.830%	$103.4567	$103.46	$103.45	$103.50
Purchase #7	$209.69	13.816%	$238.6608	$238.66	$238.65	$238.70
7 purchase totals =	$918.98		$998.3383	$998.33	$998.30	$998.40