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	$147.54	11.320%	$164.2415	$164.24	$164.25	$164.20
Purchase #2	$145.67	7.335%	$156.3549	$156.35	$156.35	$156.40
Purchase #3	$61.27	5.645%	$64.7287	$64.73	$64.75	$64.70
Purchase #4	$64.78	8.856%	$70.5169	$70.52	$70.50	$70.50
Purchase #5	$112.93	3.442%	$116.8171	$116.82	$116.80	$116.80
Purchase #6	$85.65	4.322%	$89.3518	$89.35	$89.35	$89.40
Purchase #7	$63.95	11.771%	$71.4776	$71.48	$71.50	$71.50
7 purchase totals =	$681.79		$733.4885	$733.49	$733.50	$733.50