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	$223.30	5.822%	$236.3005	$236.30	$236.30	$236.30
Purchase #2	$210.78	9.747%	$231.3247	$231.32	$231.30	$231.30
Purchase #3	$180.54	4.661%	$188.955	$188.96	$188.95	$189.00
Purchase #4	$106.32	12.201%	$119.2921	$119.29	$119.30	$119.30
Purchase #5	$67.51	6.529%	$71.9177	$71.92	$71.90	$71.90
Purchase #6	$89.89	7.482%	$96.6156	$96.62	$96.60	$96.60
Purchase #7	$64.56	11.148%	$71.7571	$71.76	$71.75	$71.80
7 purchase totals =	$942.90		$1,016.1627	$1,016.17	$1,016.10	$1,016.20