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	$102.60	4.197%	$106.9061	$106.91	$106.90	$106.90
Purchase #2	$39.46	4.612%	$41.2799	$41.28	$41.30	$41.30
Purchase #3	$22.95	10.351%	$25.3256	$25.33	$25.35	$25.30
Purchase #4	$179.61	3.284%	$185.5084	$185.51	$185.50	$185.50
Purchase #5	$115.28	3.314%	$119.1004	$119.10	$119.10	$119.10
Purchase #6	$240.62	3.589%	$249.2559	$249.26	$249.25	$249.30
Purchase #7	$92.44	7.508%	$99.3804	$99.38	$99.40	$99.40
7 purchase totals =	$792.96		$826.7567	$826.77	$826.80	$826.80