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	$69.51	4.393%	$72.5636	$72.56	$72.55	$72.60
Purchase #2	$237.79	8.722%	$258.53	$258.53	$258.55	$258.50
Purchase #3	$88.98	4.873%	$93.316	$93.32	$93.30	$93.30
Purchase #4	$190.78	10.330%	$210.4876	$210.49	$210.50	$210.50
Purchase #5	$85.66	12.253%	$96.1559	$96.16	$96.15	$96.20
Purchase #6	$101.38	12.404%	$113.9552	$113.96	$113.95	$114.00
Purchase #7	$131.27	13.874%	$149.4824	$149.48	$149.50	$149.50
7 purchase totals =	$905.37		$994.4907	$994.50	$994.50	$994.60