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	$75.96	13.589%	$86.2822	$86.28	$86.30	$86.30
Purchase #2	$78.46	8.178%	$84.8765	$84.88	$84.90	$84.90
Purchase #3	$78.92	13.468%	$89.5489	$89.55	$89.55	$89.50
Purchase #4	$162.38	8.317%	$175.8851	$175.89	$175.90	$175.90
Purchase #5	$185.44	3.568%	$192.0565	$192.06	$192.05	$192.10
Purchase #6	$145.49	6.355%	$154.7359	$154.74	$154.75	$154.70
Purchase #7	$248.84	6.139%	$264.1163	$264.12	$264.10	$264.10
7 purchase totals =	$975.49		$1,047.5014	$1,047.52	$1,047.55	$1,047.50