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	$74.89	5.632%	$79.1078	$79.11	$79.10	$79.10
Purchase #2	$89.78	12.282%	$100.8068	$100.81	$100.80	$100.80
Purchase #3	$70.26	11.740%	$78.5085	$78.51	$78.50	$78.50
Purchase #4	$156.28	6.259%	$166.0616	$166.06	$166.05	$166.10
Purchase #5	$167.79	9.615%	$183.923	$183.92	$183.90	$183.90
Purchase #6	$183.71	6.577%	$195.7926	$195.79	$195.80	$195.80
Purchase #7	$201.79	8.720%	$219.3861	$219.39	$219.40	$219.40
7 purchase totals =	$944.50		$1,023.5864	$1,023.59	$1,023.55	$1,023.60