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	$57.69	7.332%	$61.9198	$61.92	$61.90	$61.90
Purchase #2	$232.98	5.460%	$245.7007	$245.70	$245.70	$245.70
Purchase #3	$85.74	12.782%	$96.6993	$96.70	$96.70	$96.70
Purchase #4	$159.27	9.150%	$173.8432	$173.84	$173.85	$173.80
Purchase #5	$52.69	12.466%	$59.2583	$59.26	$59.25	$59.30
Purchase #6	$75.55	5.258%	$79.5224	$79.52	$79.50	$79.50
Purchase #7	$218.64	3.300%	$225.8551	$225.86	$225.85	$225.90
7 purchase totals =	$882.56		$942.7988	$942.80	$942.75	$942.80