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	$94.33	9.834%	$103.6064	$103.61	$103.60	$103.60
Purchase #2	$82.64	12.555%	$93.0155	$93.02	$93.00	$93.00
Purchase #3	$145.41	8.874%	$158.3137	$158.31	$158.30	$158.30
Purchase #4	$144.49	8.538%	$156.8266	$156.83	$156.85	$156.80
Purchase #5	$227.46	7.770%	$245.1336	$245.13	$245.15	$245.10
Purchase #6	$183.99	4.129%	$191.5869	$191.59	$191.60	$191.60
Purchase #7	$64.59	11.449%	$71.9849	$71.98	$72.00	$72.00
7 purchase totals =	$942.91		$1,020.4676	$1,020.47	$1,020.50	$1,020.40