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	$146.55	4.306%	$152.8604	$152.86	$152.85	$152.90
Purchase #2	$52.41	5.200%	$55.1353	$55.14	$55.15	$55.10
Purchase #3	$173.46	6.796%	$185.2483	$185.25	$185.25	$185.20
Purchase #4	$32.63	11.423%	$36.3573	$36.36	$36.35	$36.40
Purchase #5	$27.38	3.585%	$28.3616	$28.36	$28.35	$28.40
Purchase #6	$79.73	3.341%	$82.3938	$82.39	$82.40	$82.40
Purchase #7	$234.32	12.458%	$263.5116	$263.51	$263.50	$263.50
7 purchase totals =	$746.48		$803.8683	$803.87	$803.85	$803.90