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	$185.37	3.331%	$191.5447	$191.54	$191.55	$191.50
Purchase #2	$209.69	12.826%	$236.5848	$236.58	$236.60	$236.60
Purchase #3	$48.40	10.586%	$53.5236	$53.52	$53.50	$53.50
Purchase #4	$236.82	5.845%	$250.6621	$250.66	$250.65	$250.70
Purchase #5	$152.63	13.229%	$172.8214	$172.82	$172.80	$172.80
Purchase #6	$25.39	12.795%	$28.6387	$28.64	$28.65	$28.60
Purchase #7	$195.49	10.412%	$215.8444	$215.84	$215.85	$215.80
7 purchase totals =	$1,053.79		$1,149.6197	$1,149.60	$1,149.60	$1,149.50