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	$49.56	3.799%	$51.4428	$51.44	$51.45	$51.40
Purchase #2	$57.96	5.748%	$61.2915	$61.29	$61.30	$61.30
Purchase #3	$41.83	13.159%	$47.3344	$47.33	$47.35	$47.30
Purchase #4	$247.39	6.860%	$264.361	$264.36	$264.35	$264.40
Purchase #5	$47.60	5.524%	$50.2294	$50.23	$50.25	$50.20
Purchase #6	$74.96	13.819%	$85.3187	$85.32	$85.30	$85.30
Purchase #7	$195.86	5.489%	$206.6108	$206.61	$206.60	$206.60
7 purchase totals =	$715.16		$766.5886	$766.58	$766.60	$766.50