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	$114.73	11.512%	$127.9377	$127.94	$127.95	$127.90
Purchase #2	$234.26	12.827%	$264.3085	$264.31	$264.30	$264.30
Purchase #3	$105.99	3.195%	$109.3764	$109.38	$109.40	$109.40
Purchase #4	$156.63	5.459%	$165.1804	$165.18	$165.20	$165.20
Purchase #5	$99.46	13.750%	$113.1358	$113.14	$113.15	$113.10
Purchase #6	$11.97	13.706%	$13.6106	$13.61	$13.60	$13.60
Purchase #7	$238.61	7.694%	$256.9687	$256.97	$256.95	$257.00
7 purchase totals =	$961.65		$1,050.5181	$1,050.53	$1,050.55	$1,050.50