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	$223.79	6.498%	$238.3319	$238.33	$238.35	$238.30
Purchase #2	$120.73	3.500%	$124.9556	$124.96	$124.95	$125.00
Purchase #3	$162.57	12.624%	$183.0928	$183.09	$183.10	$183.10
Purchase #4	$151.95	6.648%	$162.0516	$162.05	$162.05	$162.10
Purchase #5	$82.86	7.485%	$89.0621	$89.06	$89.05	$89.10
Purchase #6	$232.91	3.161%	$240.2723	$240.27	$240.25	$240.30
Purchase #7	$7.27	5.247%	$7.6515	$7.65	$7.65	$7.70
7 purchase totals =	$982.08		$1,045.4178	$1,045.41	$1,045.40	$1,045.60