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	$183.94	4.306%	$191.8605	$191.86	$191.85	$191.90
Purchase #2	$82.44	4.463%	$86.1193	$86.12	$86.10	$86.10
Purchase #3	$169.31	12.200%	$189.9658	$189.97	$189.95	$190.00
Purchase #4	$13.63	6.589%	$14.5281	$14.53	$14.55	$14.50
Purchase #5	$201.88	10.620%	$223.3197	$223.32	$223.30	$223.30
Purchase #6	$238.25	6.251%	$253.143	$253.14	$253.15	$253.10
Purchase #7	$183.57	7.295%	$196.9614	$196.96	$196.95	$197.00
7 purchase totals =	$1,073.02		$1,155.8978	$1,155.90	$1,155.85	$1,155.90