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	$151.69	8.282%	$164.253	$164.25	$164.25	$164.30
Purchase #2	$107.31	8.223%	$116.1341	$116.13	$116.15	$116.10
Purchase #3	$82.31	3.318%	$85.041	$85.04	$85.05	$85.00
Purchase #4	$155.63	5.574%	$164.3048	$164.30	$164.30	$164.30
Purchase #5	$174.44	10.740%	$193.1749	$193.17	$193.15	$193.20
Purchase #6	$74.49	6.702%	$79.4823	$79.48	$79.50	$79.50
Purchase #7	$80.35	11.278%	$89.4119	$89.41	$89.40	$89.40
7 purchase totals =	$826.22		$891.8020	$891.78	$891.80	$891.80