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	$188.63	3.871%	$195.9319	$195.93	$195.95	$195.90
Purchase #2	$96.81	6.757%	$103.3515	$103.35	$103.35	$103.40
Purchase #3	$38.57	8.194%	$41.7304	$41.73	$41.75	$41.70
Purchase #4	$110.28	12.221%	$123.7573	$123.76	$123.75	$123.80
Purchase #5	$115.88	6.850%	$123.8178	$123.82	$123.80	$123.80
Purchase #6	$207.59	10.423%	$229.2271	$229.23	$229.25	$229.20
Purchase #7	$113.40	13.370%	$128.5616	$128.56	$128.55	$128.60
7 purchase totals =	$871.16		$946.3776	$946.38	$946.40	$946.40