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	$67.33	8.502%	$73.0544	$73.05	$73.05	$73.10
Purchase #2	$95.40	3.768%	$98.9947	$98.99	$99.00	$99.00
Purchase #3	$174.84	12.607%	$196.8821	$196.88	$196.90	$196.90
Purchase #4	$101.90	7.252%	$109.2898	$109.29	$109.30	$109.30
Purchase #5	$121.87	6.720%	$130.0597	$130.06	$130.05	$130.10
Purchase #6	$243.32	13.589%	$276.3848	$276.38	$276.40	$276.40
Purchase #7	$155.32	8.286%	$168.1898	$168.19	$168.20	$168.20
7 purchase totals =	$959.98		$1,052.8553	$1,052.84	$1,052.90	$1,053.00