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	$165.60	10.593%	$183.142	$183.14	$183.15	$183.10
Purchase #2	$159.29	5.636%	$168.2676	$168.27	$168.25	$168.30
Purchase #3	$144.49	5.721%	$152.7563	$152.76	$152.75	$152.80
Purchase #4	$189.90	13.279%	$215.1168	$215.12	$215.10	$215.10
Purchase #5	$58.98	5.819%	$62.412	$62.41	$62.40	$62.40
Purchase #6	$123.45	13.663%	$140.317	$140.32	$140.30	$140.30
Purchase #7	$124.38	4.409%	$129.8639	$129.86	$129.85	$129.90
7 purchase totals =	$966.09		$1,051.8756	$1,051.88	$1,051.80	$1,051.90