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	$136.82	11.279%	$152.2519	$152.25	$152.25	$152.30
Purchase #2	$78.59	4.704%	$82.2869	$82.29	$82.30	$82.30
Purchase #3	$198.62	13.498%	$225.4297	$225.43	$225.45	$225.40
Purchase #4	$98.48	4.706%	$103.1145	$103.11	$103.10	$103.10
Purchase #5	$14.76	13.122%	$16.6968	$16.70	$16.70	$16.70
Purchase #6	$201.36	4.478%	$210.3769	$210.38	$210.40	$210.40
Purchase #7	$213.92	13.217%	$242.1938	$242.19	$242.20	$242.20
7 purchase totals =	$942.55		$1,032.3505	$1,032.35	$1,032.40	$1,032.40