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	$160.29	3.418%	$165.7687	$165.77	$165.75	$165.80
Purchase #2	$89.78	7.466%	$96.483	$96.48	$96.50	$96.50
Purchase #3	$100.83	10.838%	$111.758	$111.76	$111.75	$111.80
Purchase #4	$168.69	11.232%	$187.6373	$187.64	$187.65	$187.60
Purchase #5	$202.33	4.681%	$211.8011	$211.80	$211.80	$211.80
Purchase #6	$84.89	9.400%	$92.8697	$92.87	$92.85	$92.90
Purchase #7	$9.83	4.194%	$10.2423	$10.24	$10.25	$10.20
7 purchase totals =	$816.64		$876.5601	$876.56	$876.55	$876.60