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	$90.57	10.352%	$99.9458	$99.95	$99.95	$99.90
Purchase #2	$130.88	7.281%	$140.4094	$140.41	$140.40	$140.40
Purchase #3	$86.65	11.757%	$96.8374	$96.84	$96.85	$96.80
Purchase #4	$213.35	9.240%	$233.0635	$233.06	$233.05	$233.10
Purchase #5	$209.55	9.148%	$228.7196	$228.72	$228.70	$228.70
Purchase #6	$171.73	6.209%	$182.3927	$182.39	$182.40	$182.40
Purchase #7	$89.29	7.383%	$95.8823	$95.88	$95.90	$95.90
7 purchase totals =	$992.02		$1,077.2507	$1,077.25	$1,077.25	$1,077.20