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	$37.91	7.814%	$40.8723	$40.87	$40.85	$40.90
Purchase #2	$226.32	12.544%	$254.7096	$254.71	$254.70	$254.70
Purchase #3	$49.71	8.252%	$53.8121	$53.81	$53.80	$53.80
Purchase #4	$159.78	13.229%	$180.9173	$180.92	$180.90	$180.90
Purchase #5	$247.55	9.601%	$271.3173	$271.32	$271.30	$271.30
Purchase #6	$162.78	9.797%	$178.7276	$178.73	$178.75	$178.70
Purchase #7	$119.81	6.192%	$127.2286	$127.23	$127.25	$127.20
7 purchase totals =	$1,003.86		$1,107.5848	$1,107.59	$1,107.55	$1,107.50