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	$153.34	3.251%	$158.3251	$158.33	$158.35	$158.30
Purchase #2	$79.62	13.492%	$90.3623	$90.36	$90.35	$90.40
Purchase #3	$18.46	11.786%	$20.6357	$20.64	$20.65	$20.60
Purchase #4	$126.78	3.351%	$131.0284	$131.03	$131.05	$131.00
Purchase #5	$212.76	9.362%	$232.6786	$232.68	$232.70	$232.70
Purchase #6	$221.55	3.741%	$229.8382	$229.84	$229.85	$229.80
Purchase #7	$54.47	12.676%	$61.3746	$61.37	$61.35	$61.40
7 purchase totals =	$866.98		$924.2429	$924.25	$924.30	$924.20