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	$99.97	9.304%	$109.2712	$109.27	$109.25	$109.30
Purchase #2	$171.69	11.428%	$191.3107	$191.31	$191.30	$191.30
Purchase #3	$60.62	6.522%	$64.5736	$64.57	$64.55	$64.60
Purchase #4	$235.47	11.809%	$263.2767	$263.28	$263.30	$263.30
Purchase #5	$89.77	6.749%	$95.8286	$95.83	$95.85	$95.80
Purchase #6	$98.81	3.481%	$102.2496	$102.25	$102.25	$102.20
Purchase #7	$93.25	13.808%	$106.126	$106.13	$106.15	$106.10
7 purchase totals =	$849.58		$932.6364	$932.64	$932.65	$932.60