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	$100.25	5.651%	$105.9151	$105.92	$105.90	$105.90
Purchase #2	$52.80	7.414%	$56.7146	$56.71	$56.70	$56.70
Purchase #3	$79.66	10.576%	$88.0848	$88.08	$88.10	$88.10
Purchase #4	$132.97	13.772%	$151.2826	$151.28	$151.30	$151.30
Purchase #5	$186.54	13.819%	$212.318	$212.32	$212.30	$212.30
Purchase #6	$189.96	3.652%	$196.8973	$196.90	$196.90	$196.90
Purchase #7	$91.58	5.381%	$96.5079	$96.51	$96.50	$96.50
7 purchase totals =	$833.76		$907.7203	$907.72	$907.70	$907.70