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	$32.92	6.483%	$35.0542	$35.05	$35.05	$35.10
Purchase #2	$182.72	4.478%	$190.9022	$190.90	$190.90	$190.90
Purchase #3	$105.98	4.713%	$110.9748	$110.97	$110.95	$111.00
Purchase #4	$170.91	7.208%	$183.2292	$183.23	$183.25	$183.20
Purchase #5	$95.61	11.810%	$106.9015	$106.90	$106.90	$106.90
Purchase #6	$167.68	8.436%	$181.8255	$181.83	$181.85	$181.80
Purchase #7	$168.53	13.608%	$191.4636	$191.46	$191.45	$191.50
7 purchase totals =	$924.35		$1,000.3510	$1,000.34	$1,000.35	$1,000.40