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	$215.73	3.783%	$223.8911	$223.89	$223.90	$223.90
Purchase #2	$120.25	3.368%	$124.3	$124.30	$124.30	$124.30
Purchase #3	$193.52	8.408%	$209.7912	$209.79	$209.80	$209.80
Purchase #4	$227.80	9.848%	$250.2337	$250.23	$250.25	$250.20
Purchase #5	$88.62	10.675%	$98.0802	$98.08	$98.10	$98.10
Purchase #6	$181.78	8.199%	$196.6841	$196.68	$196.70	$196.70
Purchase #7	$7.82	3.286%	$8.077	$8.08	$8.10	$8.10
7 purchase totals =	$1,035.52		$1,111.0573	$1,111.05	$1,111.15	$1,111.10