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	$215.59	8.415%	$233.7319	$233.73	$233.75	$233.70
Purchase #2	$62.40	12.611%	$70.2693	$70.27	$70.25	$70.30
Purchase #3	$89.28	12.317%	$100.2766	$100.28	$100.30	$100.30
Purchase #4	$23.71	6.340%	$25.2132	$25.21	$25.20	$25.20
Purchase #5	$203.95	13.300%	$231.0754	$231.08	$231.10	$231.10
Purchase #6	$53.26	11.396%	$59.3295	$59.33	$59.35	$59.30
Purchase #7	$134.97	5.506%	$142.4014	$142.40	$142.40	$142.40
7 purchase totals =	$783.16		$862.2973	$862.30	$862.35	$862.30