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	$242.76	11.498%	$270.6725	$270.67	$270.65	$270.70
Purchase #2	$95.91	3.497%	$99.264	$99.26	$99.25	$99.30
Purchase #3	$202.46	7.802%	$218.2559	$218.26	$218.25	$218.30
Purchase #4	$159.50	11.837%	$178.38	$178.38	$178.40	$178.40
Purchase #5	$89.27	4.383%	$93.1827	$93.18	$93.20	$93.20
Purchase #6	$114.37	11.638%	$127.6804	$127.68	$127.70	$127.70
Purchase #7	$175.29	12.185%	$196.6491	$196.65	$196.65	$196.60
7 purchase totals =	$1,079.56		$1,184.0846	$1,184.08	$1,184.10	$1,184.20