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	$70.70	4.568%	$73.9296	$73.93	$73.95	$73.90
Purchase #2	$7.82	3.164%	$8.0674	$8.07	$8.05	$8.10
Purchase #3	$30.47	9.330%	$33.3129	$33.31	$33.30	$33.30
Purchase #4	$49.81	13.170%	$56.37	$56.37	$56.35	$56.40
Purchase #5	$54.41	12.202%	$61.0491	$61.05	$61.05	$61.00
Purchase #6	$91.78	8.369%	$99.4611	$99.46	$99.45	$99.50
Purchase #7	$26.31	3.132%	$27.134	$27.13	$27.15	$27.10
7 purchase totals =	$331.30		$359.3241	$359.32	$359.30	$359.30