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	$98.27	7.268%	$105.4123	$105.41	$105.40	$105.40
Purchase #2	$208.79	5.506%	$220.286	$220.29	$220.30	$220.30
Purchase #3	$158.35	4.798%	$165.9476	$165.95	$165.95	$165.90
Purchase #4	$98.31	7.371%	$105.5564	$105.56	$105.55	$105.60
Purchase #5	$118.32	13.553%	$134.3559	$134.36	$134.35	$134.40
Purchase #6	$7.81	6.193%	$8.2937	$8.29	$8.30	$8.30
Purchase #7	$165.96	5.130%	$174.4737	$174.47	$174.45	$174.50
7 purchase totals =	$855.81		$914.3256	$914.33	$914.30	$914.40