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	$91.66	5.567%	$96.7627	$96.76	$96.75	$96.80
Purchase #2	$50.37	6.631%	$53.71	$53.71	$53.70	$53.70
Purchase #3	$65.28	9.248%	$71.3171	$71.32	$71.30	$71.30
Purchase #4	$180.67	5.744%	$191.0477	$191.05	$191.05	$191.00
Purchase #5	$157.92	5.129%	$166.0197	$166.02	$166.00	$166.00
Purchase #6	$50.46	10.851%	$55.9354	$55.94	$55.95	$55.90
Purchase #7	$152.56	12.688%	$171.9168	$171.92	$171.90	$171.90
7 purchase totals =	$748.92		$806.7094	$806.72	$806.65	$806.60