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	$188.52	6.364%	$200.5174	$200.52	$200.50	$200.50
Purchase #2	$216.80	6.597%	$231.1023	$231.10	$231.10	$231.10
Purchase #3	$19.27	13.787%	$21.9268	$21.93	$21.95	$21.90
Purchase #4	$98.52	11.413%	$109.7641	$109.76	$109.75	$109.80
Purchase #5	$249.96	13.194%	$282.9397	$282.94	$282.95	$282.90
Purchase #6	$116.61	9.455%	$127.6355	$127.64	$127.65	$127.60
Purchase #7	$173.57	11.399%	$193.3552	$193.36	$193.35	$193.40
7 purchase totals =	$1,063.25		$1,167.2410	$1,167.25	$1,167.25	$1,167.20