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	$81.26	9.601%	$89.0618	$89.06	$89.05	$89.10
Purchase #2	$104.42	13.668%	$118.6921	$118.69	$118.70	$118.70
Purchase #3	$128.78	9.636%	$141.1892	$141.19	$141.20	$141.20
Purchase #4	$180.58	6.103%	$191.6008	$191.60	$191.60	$191.60
Purchase #5	$88.69	13.229%	$100.4228	$100.42	$100.40	$100.40
Purchase #6	$162.94	11.377%	$181.4777	$181.48	$181.50	$181.50
Purchase #7	$229.50	7.673%	$247.1095	$247.11	$247.10	$247.10
7 purchase totals =	$976.17		$1,069.5539	$1,069.55	$1,069.55	$1,069.60