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	$117.98	10.860%	$130.7926	$130.79	$130.80	$130.80
Purchase #2	$174.72	9.265%	$190.9078	$190.91	$190.90	$190.90
Purchase #3	$184.93	3.359%	$191.1418	$191.14	$191.15	$191.10
Purchase #4	$223.74	9.250%	$244.436	$244.44	$244.45	$244.40
Purchase #5	$134.47	13.459%	$152.5683	$152.57	$152.55	$152.60
Purchase #6	$80.87	3.586%	$83.77	$83.77	$83.75	$83.80
Purchase #7	$156.46	8.178%	$169.2553	$169.26	$169.25	$169.30
7 purchase totals =	$1,073.17		$1,162.8718	$1,162.88	$1,162.85	$1,162.90