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	$206.41	7.748%	$222.4026	$222.40	$222.40	$222.40
Purchase #2	$49.27	13.119%	$55.7337	$55.73	$55.75	$55.70
Purchase #3	$158.56	13.780%	$180.4096	$180.41	$180.40	$180.40
Purchase #4	$72.59	6.675%	$77.4354	$77.44	$77.45	$77.40
Purchase #5	$162.89	6.368%	$173.2628	$173.26	$173.25	$173.30
Purchase #6	$89.56	10.223%	$98.7157	$98.72	$98.70	$98.70
Purchase #7	$181.38	11.527%	$202.2877	$202.29	$202.30	$202.30
7 purchase totals =	$920.66		$1,010.2475	$1,010.25	$1,010.25	$1,010.20