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	$208.39	10.848%	$230.9961	$231.00	$231.00	$231.00
Purchase #2	$61.36	6.788%	$65.5251	$65.53	$65.55	$65.50
Purchase #3	$185.61	3.140%	$191.4382	$191.44	$191.45	$191.40
Purchase #4	$198.54	3.277%	$205.0462	$205.05	$205.05	$205.00
Purchase #5	$48.64	7.545%	$52.3099	$52.31	$52.30	$52.30
Purchase #6	$165.28	10.243%	$182.2096	$182.21	$182.20	$182.20
Purchase #7	$223.71	7.515%	$240.5218	$240.52	$240.50	$240.50
7 purchase totals =	$1,091.53		$1,168.0469	$1,168.06	$1,168.05	$1,167.90