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	$239.68	12.348%	$269.2757	$269.28	$269.30	$269.30
Purchase #2	$129.34	11.426%	$144.1184	$144.12	$144.10	$144.10
Purchase #3	$7.36	9.361%	$8.049	$8.05	$8.05	$8.00
Purchase #4	$51.28	9.736%	$56.2726	$56.27	$56.25	$56.30
Purchase #5	$54.74	9.457%	$59.9168	$59.92	$59.90	$59.90
Purchase #6	$145.38	3.398%	$150.32	$150.32	$150.30	$150.30
Purchase #7	$97.68	7.544%	$105.049	$105.05	$105.05	$105.00
7 purchase totals =	$725.46		$793.0015	$793.01	$792.95	$792.90