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	$134.88	8.809%	$146.7616	$146.76	$146.75	$146.80
Purchase #2	$202.80	11.603%	$226.3309	$226.33	$226.35	$226.30
Purchase #3	$91.61	9.444%	$100.2616	$100.26	$100.25	$100.30
Purchase #4	$231.44	3.768%	$240.1607	$240.16	$240.15	$240.20
Purchase #5	$120.63	6.842%	$128.8835	$128.88	$128.90	$128.90
Purchase #6	$104.64	4.479%	$109.3268	$109.33	$109.35	$109.30
Purchase #7	$53.75	6.487%	$57.2368	$57.24	$57.25	$57.20
7 purchase totals =	$939.75		$1,008.9619	$1,008.96	$1,009.00	$1,009.00