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	$61.73	9.752%	$67.7499	$67.75	$67.75	$67.70
Purchase #2	$221.50	7.808%	$238.7947	$238.79	$238.80	$238.80
Purchase #3	$184.95	13.827%	$210.523	$210.52	$210.50	$210.50
Purchase #4	$50.94	8.606%	$55.3239	$55.32	$55.30	$55.30
Purchase #5	$103.30	8.484%	$112.064	$112.06	$112.05	$112.10
Purchase #6	$232.32	13.224%	$263.042	$263.04	$263.05	$263.00
Purchase #7	$57.46	13.618%	$65.2849	$65.28	$65.30	$65.30
7 purchase totals =	$912.20		$1,012.7824	$1,012.76	$1,012.75	$1,012.70