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	$171.58	11.567%	$191.4267	$191.43	$191.45	$191.40
Purchase #2	$8.27	6.593%	$8.8152	$8.82	$8.80	$8.80
Purchase #3	$212.89	4.568%	$222.6148	$222.61	$222.60	$222.60
Purchase #4	$243.59	8.383%	$264.0101	$264.01	$264.00	$264.00
Purchase #5	$169.68	8.459%	$184.0332	$184.03	$184.05	$184.00
Purchase #6	$160.29	4.871%	$168.0977	$168.10	$168.10	$168.10
Purchase #7	$125.64	4.521%	$131.3202	$131.32	$131.30	$131.30
7 purchase totals =	$1,091.94		$1,170.3179	$1,170.32	$1,170.30	$1,170.20