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	$162.48	11.502%	$181.1684	$181.17	$181.15	$181.20
Purchase #2	$189.52	11.515%	$211.3432	$211.34	$211.35	$211.30
Purchase #3	$107.78	5.665%	$113.8857	$113.89	$113.90	$113.90
Purchase #4	$181.36	5.348%	$191.0591	$191.06	$191.05	$191.10
Purchase #5	$85.56	7.298%	$91.8042	$91.80	$91.80	$91.80
Purchase #6	$156.78	3.485%	$162.2438	$162.24	$162.25	$162.20
Purchase #7	$148.68	11.545%	$165.8451	$165.85	$165.85	$165.80
7 purchase totals =	$1,032.16		$1,117.3495	$1,117.35	$1,117.35	$1,117.30