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	$69.86	3.142%	$72.055	$72.06	$72.05	$72.10
Purchase #2	$54.72	11.659%	$61.0998	$61.10	$61.10	$61.10
Purchase #3	$102.76	3.300%	$106.1511	$106.15	$106.15	$106.20
Purchase #4	$117.74	4.668%	$123.2361	$123.24	$123.25	$123.20
Purchase #5	$179.74	6.648%	$191.6891	$191.69	$191.70	$191.70
Purchase #6	$187.40	3.541%	$194.0358	$194.04	$194.05	$194.00
Purchase #7	$118.63	7.715%	$127.7823	$127.78	$127.80	$127.80
7 purchase totals =	$830.85		$876.0492	$876.06	$876.10	$876.10