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	$191.32	6.169%	$203.1225	$203.12	$203.10	$203.10
Purchase #2	$90.98	5.251%	$95.7574	$95.76	$95.75	$95.80
Purchase #3	$160.73	6.644%	$171.4089	$171.41	$171.40	$171.40
Purchase #4	$199.61	11.623%	$222.8107	$222.81	$222.80	$222.80
Purchase #5	$104.35	4.558%	$109.1063	$109.11	$109.10	$109.10
Purchase #6	$217.28	6.440%	$231.2728	$231.27	$231.25	$231.30
Purchase #7	$165.29	7.857%	$178.2768	$178.28	$178.30	$178.30
7 purchase totals =	$1,129.56		$1,211.7554	$1,211.76	$1,211.70	$1,211.80